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The present study is to investigate the isothermal oxidation behavior of Inconel 718 (a Cr/Ni/Mo/Si-based alloy) because of their excellent thermo-mechanical properties, which are important in aerospace applications. X-ray diffraction (XRD) study confirmed the formation of spinel element of NiCr 2 O 4 along with Cr 2 Ni 3 at 1000 °C. X-ray photoelectron spectroscopy (XPS) is used to define the elemental composition of oxides and Raman spectroscopy to ascertain the state of oxides. Different morphologies such as tetragonal biaxial pyramids, flakes, and polygonal plates were observed on heated samples. Cross-sectional and EDS studies clearly revealed the drastic increase of oxide layer from 800 °C to 1200 °C. Finally, electrochemical impedance spectroscopy (EIS) analysis was carried out at 800 °C, 1000 °C and 1200 °C with a tenant period and ramping rate of 24 h and 10 min respectively. The EIS results divulged that charge transfer resistance values drastically increased with increasing temperature due to oxide layer. [ABSTRACT FROM AUTHOR]

The objective of the study was to assess the levels of neutralizing antibody after COVID vaccination in the elderly and compare it with that of the younger persons. The study also aimed at determining the association between the age, sex, and comorbidities and levels of neutralizing antibodies in the young and the old. Subjects and Methods: This was a single-center, cross-sectional, analytical study, conducted in the General Medicine Unit of ACS Medical College, Chennai, from August 2021 to October 2021. Forty‑five elderly persons aged 60 years and above and 103 young adults aged 18 years and above and <60 years who were vaccinated with either COVISHIELD or COVAXIN were randomly selected to participate in this study. A detailed history regarding vaccination status, vaccination type, comorbidities, and breakthrough infection was obtained. Blood samples were collected from the participants to analyze the levels of neutralizing antibodies developed after COVID vaccination. Results: The mean age of the older participants was 66.13 ± 5.3 years and the mean age of the younger participants was 36.48 ± 10.9 years. The median level of neutralizing antibody in the younger participants was 97.4% (interquartile range [IQR]: 96.4%–98.0%) and in the older participants was 97.1% (IQR: 93.1%–97.6%). There was a significant difference in the neutralizing antibody level between the younger and the older participants (P = 0.033). There was no significant difference in the neutralizing antibody levels after two doses of either of the two vaccines among both the groups of participants. There was no significant association between the neutralizing antibody titer and sex and comorbidities in both the groups of participants. Five young and two old participants had breakthrough infections after vaccination. The antibody level was higher in persons with breakthrough infection than in those with no breakthrough infection in both the study groups. Conclusion: There was a significant difference in the neutralizing antibody level between the younger and the older participants after COVID vaccination. No significant difference existed in neutralizing antibody response with respect to the type of vaccine in both the study groups. There was no significant association between sex, comorbid status, and neutralizing antibody levels in both the groups. [ABSTRACT FROM AUTHOR]

Ultra Violet Imaging Telescope (UVIT) is one of the 5 instruments on AstroSat satellite, which was launched on September 28, 2015. UVIT was designed to make images with a resolution of < 1. 8 ′ ′ , simultaneously in two ultraviolet channels: Far Ultraviolet (130–180 nm) and Near Ultraviolet (200–300 nm). Images are also made in visible region (320–550 nm) for tracking drifts in pointing. The shortest wavelengths to be observed with UVIT can be heavily absorbed by mono-molecular deposits/contamination on the optical surfaces. Keeping contamination under control in UVIT was a major challenge and it required a variety of actions: (i) strict control of the payload materials and process, (ii) mechanical configuration, (iii) baking of all the parts to release all the adsorbed molecules etc., (iv) assembly in ultra cleanrooms, (v) pre-inspection and auditing of all the areas, in which UVIT was placed, for any potential for contamination, (vi) continuous purging, with ultra-pure nitrogen gas, till a few days before the launch, etc. In order to minimise any possible cross contaminations from the other payloads/satellite, the doors of UVIT were opened 2 months after the launch. The high performance in the orbit and high stability of the sensitivity over 4 years in the orbit shows that the contamination was negligible. This paper presents the processes and protocols followed during the integration and testing phase to minimise the contamination in order to prevent any performance degradation. [ABSTRACT FROM AUTHOR]

The present work discusses astronomical site survey reports on dust content, vertical distribution of atmospheric turbulence, precipitable water vapor (PWV), surface and upper-air data, and their effects on seeing over the Indian Astronomical Observatory (IAO) Hanle. Using Laser Particulate Counter, ambient dust measurements at various sizes (0.3 μm to 25 μm) were performed at various locations at the site during November 2015. Estimated volume concentration for the particle size at 0.5 μm was around 10,000 per cubic foot, which is equivalent to ten thousand class of clean room standard protocol. During the measurement, surface wind speed varied from 0-20 m s , while estimated aerosol optical depth (AOD) using Sky radiometer (Prede) varied from 0.02-0.04 at 500 nm, which indicates the site is fairly clean. The two independent measurements of dust content and aerosol concentrations at the site agreed well. The turbulence or wind gust at the site was studied with wind profiles at three different heights above the ground. The strength of the wind gust varies with time and altitude. Nocturnal temperature across seasons varied with a moderate at summer (6−8 C) and lower in winter (4−5 C). However, the contrast between the two is significantly small due to cold and extremely dry typical climatic conditions of the site. The present study also examined the effects of surface and upper-air data along with Planetary Boundary Layer (PBL) dynamics with seeing measurement over the site. Further, a comparative study of such observed parameters was conducted with other high altitude astronomical observatories across the globe. [ABSTRACT FROM AUTHOR]

The synthesis of novel ferrocenyl spiropyrrolidines through the of azomethine ylides generated by a decarboxylative route from sarcosine and diketones with the dipolarophile, Knoevenagel adduct of ferrocene carbaldehyde is described. The regiochemistry and stereochemistry of the cycloadducts were confirmed by X-ray analysis of one of the synthesized cycloadducts. [ABSTRACT FROM AUTHOR]

• Novel in situ high temperature oxidation analysis was performed to Nb/Hf/Ti (C-103) alloy. • The formation of Nb 2 O 5 and HfO 2 are time dependent at a temperature of 800 °C. • Failure of C-103 alloy observed at 800 °C beyond 1000 sec due to higher oxidation rate. • The oxidation kinetics of C-103 follow the parabolic law of oxidation. In this study, a novel perspective method was attempted to understand the oxidation behavior of Nb/Hf/Ti (C-103) alloy at high temperature environment through in situ oxidation resistance measurement with respect to temperature and time. Electrochemical impedance spectroscopy (EIS) was employed to determine the oxidation behavior of C-103 alloy at different temperatures. Structural and chemical properties of heat treated samples were characterized by X-ray diffraction (XRD), scanning electron microscope and energy dispersive X-ray spectroscopy (SEM/EDX). EIS studies revealed that charge transfer resistance (R ct) is decreasing and at the same time current density is increasing with increasing temperature and time during high temperature oxidation process. Also, C-103 alloy obey parabolic law of corrosion during rapid heat treatment process. [ABSTRACT FROM AUTHOR]

One-pot three component synthesis of novel pyrido[1,4]-oxazepine fused spiropyrrolidines has been accomplished in good yields by 1,3-dipolar cycloaddition reaction of azomethine ylide, derived from paraformaldehyde and sarcosine with (E)-4-benzylidene-hexahydro-1H-pyrido[2,1-c][1,4]-oxazepine-3(7H)-one as dipolarophiles derived from Baylis-Hillman adducts. The effect of solvent on the [3 + 2]-cycloaddition reaction is also studied. [ABSTRACT FROM AUTHOR]

ADITYA-L1 is India's first dedicated mission to observe the Sun and its atmosphere from a halo orbit around L1 point. Visible emission line coronagraph (VELC) is the primary payload on board Aditya-L1 to observe the Sun's corona. VELC is designed as an internally occulted reflective coronagraph to meet the observational requirements of wide wavelength band and the field of view close to the solar limb (1.05 R Sun ). Images of the solar corona in continuum and spectra in three emission lines 5303 Å [Fe xiv], 7892 Å [Fe xi] and 10747 Å [Fe xiii] obtained with high cadence are to be analyzed using software algorithms automatically. A reasonable part of these observations will be made in a synoptic mode in which the data are processed through a standard pipeline and the resulting products will be made available for public use. The procedure involves the calibration of instrument and detectors, converting the images into the FITS format, correcting the images and spectra for the instrumental effects, and aligning the images (in terms of position angles and image scales) etc. Then, develop image processing algorithms to detect the occurrence of energetic events using continuum images. Also derive physical parameters, such as temperature and velocity structure of solar corona using emission line observations. Here, we describe the calibration of detectors and the development of software algorithms to detect the occurrence of CMEs and analyze the spectroscopic data. [ABSTRACT FROM AUTHOR]

One of the major objectives of the optomechanics is to support large optics required for the purpose and also to maintain high dynamic stability in operation. This requirement calls for more number of supports, to support large optics. While addressing this issue, the mounting system tends to become non-kinematic and distorts the optical surface and leads to poor image quality. The distorted optical surfaces bring in increased RMS surface wavefront errors which will result in poor image quality. In this context, a new concept is proposed in our previous publication (Nagabhushana et al., 2021) which involves introduction of deformable bushes at the optomechanical interfaces. These are deformed by applied clamping forces and also enabling all degrees of freedom (DOF) to be arrested. This also ensures that the clamping force in axial DOF is limited to a minimal value. This technique enables to arrest of axial DOF without exerting the clamping force on the optomechanical assembly there by reduces optical aberrations and improves the mounting system's dynamic stability. This is because deformable bushes absorb all the clamping forces and the strain has no impact on the mount and therefore does not lead deformation of the optical surface. The clamping forces are simulated by Finite Element (FE) methods. Further, in this paper, the concept is verified and validated by experiments. The simulation results are observed to be in close correlation with experiment results. Improved stability is also observed by additional constraints introduced to optomechanical mounts with no compromise in wavefront errors. [ABSTRACT FROM AUTHOR]

Over the last 5 years, UVIT has completed observations of more than 500 proposals with ∼ 800 unique pointings. In addition, regular planned monitoring observations have been made and from their analysis various key parameters related to in orbit performance of UVIT have been quantified. The sensitivities of the UV channels have remained steady indicating no effect of potential molecular contamination confirming the adequacy of all the protocols implemented for avoiding contamination. The quality of the PSF through the years confirms adequacy of thermal control measures. The early calibrations obtained during the Performance Verification (PV) phase have been further revised for more subtle effects. These include flat fields and detector distortions with greater precision. The operations of UVIT have also evolved through in orbit experience, e.g. tweaking of operational sequencing, protocol for recovery from bright object detection (BOD) shutdowns, parameters for BOD thresholds, etc. Finally, some effects of charged particle hits on electronics led to opimised strategy for regular resetting. The Near-UV channel was lost in one of such operations. All the above in-orbit experiences are presented here. [ABSTRACT FROM AUTHOR]

The performance of the ultraviolet telescope (UVIT) on-board AstroSat is reported. The performance in orbit is also compared with estimates made from the calibrations done on the ground. The sensitivity is found to be within $$\sim $$ 15% of the estimates, and the spatial resolution in the NUV is found to exceed significantly the design value of $$1.8^{\prime \prime }$$ and it is marginally better in the FUV. Images obtained from UVIT are presented to illustrate the details revealed by the high spatial resolution. The potential of multi-band observations in the ultraviolet with high spatial resolution is illustrated by some results. [ABSTRACT FROM AUTHOR]

Solar coronagraph mimics total solar eclipse by blocking the solar disk and enabling the observation of extended coronal atmosphere of the Sun. Visible Emission Line Coronagraph (VELC), on-board Aditya-L1 space mission, is an internally occulted solar coronagraph capable of simultaneous imaging, spectroscopy and spectro-polarimetry close to the solar limb. This payload is designed to study the coronal plasma and heating of the solar corona. Studying development, dynamics and origin of coronal mass ejections and measurement of coronal magnetic fields over active regions are other important science goals. VELC is designed to image the solar corona at 500 nm with an angular resolution of 5" over a field of view (FOV) of 1.05-3 Ro. It also facilitates simultaneous multi-slit spectroscopy at three emission lines, viz. Fe XIV (530.3 nm), Fe XI (789.2 nm) and Fe XIII (1074.7 nm) with a spectral resolution of 28, 31 and 202 mÅ/pixel respectively, over an FOV of 1.05-1.5 Ro. The payload has a dual-beam spectro-polarimetry channel for magnetic field measurements at 1074.7 nm. [ABSTRACT FROM AUTHOR]

The outer atmosphere of the sun - called the corona - has been observed during total solar eclipse for short periods (typically < 6 min), from as early as the eighteenth century. In the recent past, space-based instruments have permitted us to study the corona uninterruptedly. In spite of these developments, the dynamic corona and its high temperature (1-2 million K) are yet to be fully understood. It is conjectured that their dynamic nature and associated energetic events are possible reasons behind the high temperature. In order to study these in detail, a visible emission line space solar coronagraph is being proposed as a payload under the small-satellite programme of the Indian Space Research Organisation. The satellite is named as Aditya-1 and the scientific objectives of this payload are to study: (i) the existence of intensity oscillations for the study of wavedriven coronal heating; (ii) the dynamics and formation of coronal loops and temperature structure of the coronal features; (iii) the origin, cause and acceleration of coronal mass ejections (CMEs) and other solar active features, and (iv) coronal magnetic field topology and three-dimensional structures of CMEs using polarization information. The uniqueness of this payload compared to previously flown space instruments is as follows: (a) observations in the visible wavelength closer to the disk (down to 1.05 solar radii); (b) high time cadence capability (better than two-images per second), and (c) simultaneous observations of at least two spectral windows all the time and three spectral windows for short durations. [ABSTRACT FROM AUTHOR]

The Lunar Ultraviolet Cosmic Imager (LUCI) is a near-ultraviolet (NUV) telescope with all-spherical mirrors, designed and built to fly as a scientific payload on a lunar mission with Team Indus—the original Indian entry to the Google Lunar X-Prize. Observations from the Moon provide a unique opportunity of a stable platform with an unobstructed view of the space at all wavelengths due to the absence of atmosphere and ionosphere. LUCI is an 80 mm aperture telescope, with a field of view of 27.6 ′ × 20.4 ′ and a spatial resolution of 5 ″ , will scan the sky in the NUV (200–320 nm) domain to look for transient sources. We describe here the assembly, alignment, and calibration of the complete instrument. LUCI is now in storage in a class 1000 clean room and will be delivered to our flight partner in readiness for flight. [ABSTRACT FROM AUTHOR]